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Subject[PATCH v3 13/23] n_tty: Fully initialize ldisc before restarting buffer work
Date
Buffer work may already be pending when the n_tty ldisc is re-opened,
eg., when setting the ldisc (via TIOCSETD ioctl) and when hanging up
the tty. Since n_tty_set_room() may restart buffer work, first ensure
the ldisc is completely initialized.

Factor n_tty_set_room() out of reset_buffer_flags() (only 2 callers)
and reorganize n_tty_open() to set termios last; buffer work will
be restarted there if necessary, after the char_map is properly
initialized.

Fixes this WARNING:

[ 549.561769] ------------[ cut here ]------------
[ 549.598755] WARNING: at drivers/tty/n_tty.c:160 n_tty_set_room+0xff/0x130()
[ 549.604058] scheduling buffer work for halted ldisc
[ 549.607741] Pid: 9417, comm: trinity-child28 Tainted: G D W 3.7.0-next-20121217-sasha-00023-g8689ef9 #219
[ 549.652580] Call Trace:
[ 549.662754] [<ffffffff81c432cf>] ? n_tty_set_room+0xff/0x130
[ 549.665458] [<ffffffff8110cae7>] warn_slowpath_common+0x87/0xb0
[ 549.668257] [<ffffffff8110cb71>] warn_slowpath_fmt+0x41/0x50
[ 549.671007] [<ffffffff81c432cf>] n_tty_set_room+0xff/0x130
[ 549.673268] [<ffffffff81c44597>] reset_buffer_flags+0x137/0x150
[ 549.675607] [<ffffffff81c45b71>] n_tty_open+0x131/0x1c0
[ 549.677699] [<ffffffff81c47824>] tty_ldisc_open.isra.5+0x54/0x70
[ 549.680147] [<ffffffff81c482bf>] tty_ldisc_hangup+0x11f/0x1e0
[ 549.682409] [<ffffffff81c3fa17>] __tty_hangup+0x137/0x440
[ 549.684634] [<ffffffff81c3fd49>] tty_vhangup+0x9/0x10
[ 549.686443] [<ffffffff81c4a42c>] pty_close+0x14c/0x160
[ 549.688446] [<ffffffff81c41225>] tty_release+0xd5/0x490
[ 549.690460] [<ffffffff8127d8a2>] __fput+0x122/0x250
[ 549.692577] [<ffffffff8127d9d9>] ____fput+0x9/0x10
[ 549.694534] [<ffffffff811348c2>] task_work_run+0xb2/0xf0
[ 549.696349] [<ffffffff81113c6d>] do_exit+0x36d/0x580
[ 549.698286] [<ffffffff8107d964>] ? syscall_trace_enter+0x24/0x2e0
[ 549.702729] [<ffffffff81113f4a>] do_group_exit+0x8a/0xc0
[ 549.706775] [<ffffffff81113f92>] sys_exit_group+0x12/0x20
[ 549.711088] [<ffffffff83cfab18>] tracesys+0xe1/0xe6
[ 549.728001] ---[ end trace 73eb41728f11f87e ]---

Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
drivers/tty/n_tty.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 5073dd1..e269296 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -218,9 +218,8 @@ static void check_unthrottle(struct tty_struct *tty)
* Locking: tty_read_lock for read fields.
*/

-static void reset_buffer_flags(struct tty_struct *tty)
+static void reset_buffer_flags(struct n_tty_data *ldata)
{
- struct n_tty_data *ldata = tty->disc_data;
unsigned long flags;

spin_lock_irqsave(&ldata->read_lock, flags);
@@ -233,7 +232,6 @@ static void reset_buffer_flags(struct tty_struct *tty)

ldata->canon_head = ldata->canon_data = ldata->erasing = 0;
bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
- n_tty_set_room(tty);
}

static void packet_mode_flush(struct tty_struct *tty)
@@ -261,7 +259,8 @@ static void packet_mode_flush(struct tty_struct *tty)

static void n_tty_flush_buffer(struct tty_struct *tty)
{
- reset_buffer_flags(tty);
+ reset_buffer_flags(tty->disc_data);
+ n_tty_set_room(tty);

if (tty->link)
packet_mode_flush(tty);
@@ -1653,14 +1652,14 @@ static int n_tty_open(struct tty_struct *tty)
goto err_free_bufs;

tty->disc_data = ldata;
- /* indicate buffer work may resume */
- clear_bit(TTY_LDISC_HALTED, &tty->flags);
- reset_buffer_flags(tty);
- tty_unthrottle(tty);
+ reset_buffer_flags(tty->disc_data);
ldata->column = 0;
- n_tty_set_termios(tty, NULL);
tty->minimum_to_wake = 1;
tty->closing = 0;
+ /* indicate buffer work may resume */
+ clear_bit(TTY_LDISC_HALTED, &tty->flags);
+ n_tty_set_termios(tty, NULL);
+ tty_unthrottle(tty);

return 0;
err_free_bufs:
--
1.8.1.2


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